Abstract
Key messageWe discovered a natural FT-A2 allele that increases grain number per spike in both pasta and bread wheat with limited effect on heading time.Increases in wheat grain yield are necessary to meet future global food demands. A previous study showed that loss-of-function mutations in FLOWERING LOCUS T2 (FT2) increase spikelet number per spike (SNS), an important grain yield component. However, these mutations were also associated with reduced fertility, offsetting the beneficial effect of the increases in SNS on grain number. Here, we report a natural mutation resulting in an aspartic acid to alanine change at position 10 (D10A) associated with significant increases in SNS and no negative effects on fertility. Using a high-density genetic map, we delimited the SNS candidate region to a 5.2-Mb region on chromosome 3AS including 28 genes. Among them, only FT-A2 showed a non-synonymous polymorphism (D10A) present in two different populations segregating for the SNS QTL on chromosome arm 3AS. These results, together with the known effect of the ft-A2 mutations on SNS, suggest that variation in FT-A2 is the most likely cause of the observed differences in SNS. We validated the positive effects of the A10 allele on SNS, grain number, and grain yield per spike in near-isogenic tetraploid wheat lines and in an hexaploid winter wheat population. The A10 allele is present at very low frequency in durum wheat and at much higher frequency in hexaploid wheat, particularly in winter and fall-planted spring varieties. These results suggest that the FT-A2 A10 allele may be particularly useful for improving grain yield in durum wheat and fall-planted common wheat varieties.
Highlights
Wheat is a global crop of major economic value and nutritional importance as it provides around 20% of the calories and protein consumed by the human population
We identified an A to C SNP at position 124,172,909 in chromosome arm 3AS of the Chinese Spring (CS) RefSeq v1.0, which resulted in an amino acid change at position 10 of the FT-A2 protein from aspartic acid (D) to alanine (A) (D10 and A10 alleles)
We describe the change from the ancestral to the derived allele (D10A) rather than relative to the Chinese Spring (CS) reference genome that carries the derived A10 allele, We screened a collection of 417 T. turgidum ssp. durum accessions with a Cleaved Amplified Polymorphic Sequence (CAPS) marker for the D10A polymorphism and found that only 0.7% carried the A10 allele (Table 1)
Summary
Wheat is a global crop of major economic value and nutritional importance as it provides around 20% of the calories and protein consumed by the human population (http://www.fao.org/faostat/en/#data/FBS). With ever-changing environmental conditions and the rising human population, it is critical to increase wheat grain yield to meet future demands. Several genes have been identified that affect these grain yield components (Kuzay et al 2019; Li et al 2019; Poursarebani et al 2015; Sakuma et al 2019; Shaw et al 2013; Simmonds et al 2016; Wang et al 2019). Many of the genes affecting SNS have strong effects on flowering time that can limit their use in variety development.
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